1 ) Field of the Invention
The present invention relates generally to depth control systems for agricultural implements, and, more specifically, to an adjustable bracket and valve structure for such systems.
2) Related Art
Many hydraulically controlled agricultural implements utilize a single point depth control system wherein implement depth is monitored and adjusted at a single location on the implement. Typically a plunger bracket assembly is slidably mounted on an actuator tube operably connected to the implement rockshaft. A plunger on the assembly contacts a poppet valve to stop fluid flow from the hydraulic lift cylinders at a preselected depth. To adjust depth, a set screw on the bracket assembly is loosened, and the bracket assembly is slid along the tube. The screw is tightened to secure the assembly at the desired location along the tube. Normally the amount of depth adjustment is small. When the set screw is unthreaded, the bracket is loosened from the tube and slides on the tube, often to a wrong location. The bracket has to be manually moved, and the amount of adjustment has to be determined visually. When the set screw is tightened, the bracket often changes location. Several trials may be required to achieve the desired position. Therefore, depth adjustment is often imprecise, difficult to repeat, and time consuming.
In another type of depth control, which is the subject of copending and commonly assigned application Ser. No. 08/074,233, filed Jun. 9, 1993, and entitled REMOTELY ADJUSTABLE DEPTH CONTROL, a long crank is provided to adjust a linkage adjacent the depth control cylinder. Although such a device has the advantage of directly monitoring cylinder extension and retraction, the valve and linkage components are more complicated, expensive and difficult to access, and are subject to damage by crops and soil passing through the machine. Also, this type of device relies on intermittent contact between an activating cylinder pin and a portion of the system that actually controls the oil flow.